In the related art, a majority of members such as turbine blades that are used in a high-temperature environment are formed of metallic material such as nickel-based alloy or titanium-based alloy that is heat resistant material.
Furthermore, in recent years, a technology of improving the oxidation resistant characteristics of the members by forming an oxidation resistant coating layer on a surface layer of the members has been generally used.
In the technology of forming this oxidation resistant coating layer, the surface layer of a member is enriched with aluminum (the content of aluminum is increased) and this surface layer is used as the oxidation resistant layer to form the oxidation resistant coating layer.
Specific examples of a method of enriching the surface layer of the member with aluminum include a method of diffusing aluminum in the surface layer of the member, a method of thermally spraying an alloy containing a large amount of aluminum, a method of forming a film of an alloy containing a large amount of aluminum using sputtering, a plating process using molten salt or molten aluminum, and the like.
According to the method of diffusing aluminum in the surface layer of the member, aluminum is diffused in the surface layer of the member by vapor phase reaction of aluminum halide and thus an aluminum-rich oxidation resistant layer is formed.
According to the method of thermally spraying an alloy containing a large amount of aluminum, an alloy containing a large amount of aluminum is thermally sprayed to a surface of the member to make the alloy containing a large amount of aluminum be attached to the surface of the member, whereby the aluminum-rich oxidation layer is formed.
According to the method of forming a film of an alloy containing a large amount of aluminum using sputtering, an alloy containing a large amount of aluminum is deposited on the surface of the member in a manner of physical vapor deposition by using a target formed of an alloy containing a large amount of aluminum, whereby the aluminum-rich oxidation resistant layer is formed.
According to the plating process using molten salt or molten aluminum, the member is dipped in the molten aluminum, whereby the aluminum-rich oxidation layer is formed.